Sunday, November 11, 2012

Cut your brain some SLACK

Action potentials are the main means of communication between neurons, and their exact timing can be really important. But the specific timing of action potentials is really important in the auditory system, because the auditory system encodes (among other things) information about sound wave frequency.

I've previously written about auditory processing with regards to the wonder that is the chicken brain, but today we will focus on timing-specificity in the mammalian brainstem. Specifically, some weird channels in the Medial Nucleus of the Trapezoid Body (the MNTB).
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A paper from the Kaczmarek lab at Yale explains that these sodium-activated potassium channel (SLICK and SLACK) are present in the mouse auditory brainstem and contribute to the 'temporal accuracy' of the MNTB neurons. Yang et al. (2007) record the action potentials from these neurons at a range of frequencies and show that the neuron can 'keep' up with the frequencies better when more sodium is present.

In the figure above, the 'flatter' the line, the better the 'temporal accuracy.' They also made a computational model of this neuron and ran simulations altering the sodium values and reversal potential.

Yang et al., 2007 Figure 9D

Their model simulations are similar to their experimental recordings, in that more sodium results in more temporal accuary of the action potential. They confirmed that this was dues to a sodium-activated potassium channel by directly activating SLACK and seeing a similar improvement in temporal accuracy.

The SLACK channel still blows my mind, but its role in helping the auditory system fire with the utmost precision actually makes a lot of sense.

2 comments:

IIRC, the auditory system also has some special fast motor proteins in the cochlea, and some special fast synapses (also in the MNTB, I think). That's all cool for the temporal processing of sound. What I've always wondered, though, is why these fancy things aren't just everywhere? Why can't I just be built out of those extra fast motor proteins and have super reflexes? Okay, it probably wouldn't work like that, but I wonder what the benefit of some things being SLOWER is.

In this post, you described comprehensively about the action potentials as the main means of communication between neurons, and their exact timing is very important. Thank you so much for your good work. traumatic brain injury